Laser eye surgery system

ABSTRACT

A method for laser eye surgery that accommodates patient movement includes: generating a first and a second electromagnetic radiation beam, the second beam configured to modify eye tissue; propagating the first beam to a scanner along a an optical path length that changes in response to eye movement; focusing the first beam to a first focal point within the eye; scanning the first focal point at different locations within the eye; propagating a portion of the first beam reflected from the first focal point location back along the variable optical path to a sensor; generating an intensity signal indicative of the intensity of the portion of the reflected first beam; propagating the second beam to the scanner along the variable optical path; focusing the second beam to a second focal point and scanning the second focal point to create an incision in the cornea of the eye.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/191,095, filed Feb. 26, 2014, which claims priority to U.S.provisional application No. 61/780,736 filed on Mar. 13, 2013, theentire contents of all of which are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

Laser eye surgery systems have become ubiquitous and varied in purpose.For example, a laser eye surgery system may be configured to reshape theanterior surface of the cornea via ablation to effect a refractivecorrection. A laser eye surgery system may also be configured to createa corneal flap to expose an underlying portion of the cornea such thatthe underlying portion can be reshaped via ablation and then recoveredwith the flap. More recently developed laser eye surgery systems may beconfigured to create one or more incisions in the cornea or limbus toreshape the cornea, create one or more incisions in the cornea toprovide access for a cataract surgery instrument and/or to provideaccess for implantation of an intraocular lens, incise a capsulotomy inthe anterior lens capsule to provide access for removal of a cataractouslens, segment a cataractous lens, and/or incise a capsulotomy in theposterior lens capsule.

Many laser eye surgery systems generate a series of laser beam pulsesvia a laser beam source. The laser beam pulses propagate along anoptical path to the patient's eye. The optical path typically includescontrollable elements such as scanning mechanisms and/or focusingmechanisms to control the direction and/or location of the emitted laserbeam pulses relative to the patient.

Some laser eye surgery systems are configured to track eye movement(e.g., change of viewing direction of the eye) such that control overthe direction and/or location of the emitted laser beam pulses can beaccomplished so as to account for the eye movement. For example, a lasereye surgery system may optically track a feature in the eye, such as anatural feature or a fiduciary marker added to the eye, so as to trackmovement of the eye.

In contrast, other laser eye surgery systems may be configured toinhibit eye movement. For example, a contact lens may be employed thatdirectly contacts the anterior surface of the cornea so as to restraineye movement. Such restraint, however, may cause associated patientdiscomfort and/or anxiety.

Beyond eye movement, many laser eye surgery systems are configured toinhibit relative movement between the patient and the laser eye surgerysystem. For example, a laser eye surgery system may include some sort ofsubstantial patient restraint feature such as a dedicated supportassembly (e.g., chair or bed), which can include restraint featuresconfigured to inhibit movement of the patient relative to the supportassembly. Such a dedicated support assembly may include a positioningmechanism by which the patient can be moved to position the patient'seye relative to the optical path of the laser eye surgery system.Additionally, a laser eye surgery system may be configured to rigidlysupport components that determine the location of the optical path ofthe laser pulses so as to substantially prevent movement of the opticalpath relative to the dedicated support assembly, thereby also inhibitingrelative movement of the patient's eye relative to the emitted laserpulses. A dedicated support assembly and rigid support of optical pathcomponents, however, can add significant complexity and related cost toa laser eye surgery system. Additionally, the use of rigid support ofoptical path components and a dedicated patient support assembly canfail to preclude the possibility of some level of significant relativemovement between the patient and the laser eye surgery system.

Thus, laser surgery systems with improved characteristics with respectto patient movement, and related methods, would be beneficial.

SUMMARY

Imaging systems and related methods are provided that can be used insuitable laser surgery systems such as, for example, laser eye surgerysystems. In many embodiments, a system for imaging an eye of a patientis configured to accommodate relative movement of a patient whilemaintaining alignment between the patient's eye and a scannedelectromagnetic radiation beam used at least in part to image the eye.In many embodiments, the imaging system is configured to be insensitiveto optical path length variations induced by patient movement. Byaccommodating patient movement, additional system complexity and relatedcost associated with attempting to restrain movement of the patient canbe avoided. Additionally, accommodation of patient movement can beemployed to increase ease of use of a laser surgery system, such as byconfiguring the laser surgery system to be supported by a repositionablecart that can be moved adjacent to an existing patient support assembly(e.g., a non-dedicated patient support assembly such as a bed).

Thus, in one aspect, a method of imaging an eye while accommodatingpatient movement is provided. The method includes using a beam source togenerate an electromagnetic radiation beam. The electromagneticradiation beam is propagated from the beam source to a scanner along avariable optical path having an optical path length that varies inresponse to movement of the eye. The electromagnetic radiation beam isfocused to a focal point at a location within the eye. The scanner isused to scan the focal point to different locations within the eye. Aportion of the electromagnetic radiation beam reflected from the focalpoint location is propagated back along the variable optical path to asensor. The sensor is used to generate an intensity signal indicative ofthe intensity of a portion of the electromagnetic radiation beamreflected from the focal point location and propagated to the sensor.

In many embodiments of the method, one or more optical path relatedcomponents are used to accommodate patient movement. For example, themethod can further include using a first support assembly to support thescanner so as to accommodate relative movement between the scanner andthe first support assembly so as to accommodate movement of the eye. Themethod can include using a second support assembly to support the firstsupport assembly so as to accommodate relative movement between thefirst support assembly and the second support assembly so as toaccommodate movement of the eye. The method can include using the firstsupport assembly to support a first reflector configured to reflect theelectromagnetic radiation beam so as to propagate to the scanner along aportion of the variable optical path. The method can include using abase assembly to support the second support assembly so as toaccommodate relative movement between the second support assembly andthe base assembly so as to accommodate movement of the eye. The methodcan include using the second support assembly to support a secondreflector configured to reflect the electromagnetic radiation beam topropagate along a portion of the variable optical path so as to beincident on the first reflector.

In many embodiments of the method, portions of the electromagneticradiation beam reflected from locations other than the focal point areblocked to ensure that only a portion of the electromagnetic beamreflected from the focal point is used to generate the intensity signal.For example, using the sensor to generate the intensity signal caninclude passing a reflected portion of the electromagnetic radiationbeam through an aperture to block portions of the electromagneticradiation beam reflected from locations other than the focal pointlocation.

A polarization-sensitive device (e.g., a polarization beamsplitter/combiner) can be used to direct a portion of theelectromagnetic radiation beam reflected from the focal point to beincident upon a detector configured to generate the intensity signal.For example, the method can further include passing the electromagneticradiation beam through a polarization-sensitive device. The method canfurther include modifying polarization of at least one of theelectromagnetic radiation beam and a portion of the electromagneticradiation beam reflected from the focal point location. The method canfurther include using the polarization-sensitive device to reflect aportion of the electromagnetic radiation beam reflected from the focalpoint location so as to be incident upon the sensor.

In many embodiments of the method, the electromagnetic radiation beamcan be configured to so as to not modify tissue. For example, theelectromagnetic radiation beam can have an energy level below athreshold level for tissue modification. Alternatively, theelectromagnetic radiation beam can be configured to modify tissue.

The electromagnetic radiation beam can have any suitable configuration.For example, the electromagnetic radiation beam can include a pluralityof laser pulses having a wavelength between 320 nanometers and 430nanometers. As another example, the electromagnetic radiation beam caninclude a plurality of laser pulses having a wavelength between 800nanometers and 1100 nanometers.

In another aspect, an eye surgery system is provided. The systemincludes an eye interface device, a scanning assembly, a beam source, afree-floating mechanism, and a detection assembly. The eye interfacedevice is configured to interface with an eye of a patient. The scanningassembly supports the eye interface device and is operable to scan afocal point of an electromagnetic radiation beam to different locationswithin the eye. The beam source is configured to generate theelectromagnetic radiation beam. The free-floating mechanism supports thescanning assembly and is configured to accommodate movement of the eyeand provide a variable optical path for the electronic radiation beamand a portion of the electronic radiation beam reflected from the focalpoint location. The variable optical path is disposed between the beamsource and the scanner and has an optical path length that changes inresponse to movement of the eye. The detection assembly is configured togenerate an intensity signal indicative of intensity of a portion of theelectromagnetic radiation beam reflected from the focal point location.

In many embodiments of the system, the scanning assembly includes one ormore scanning devices. For example, the scanning assembly can include az-scan device and a xy-scan device. The z-scan device can be operable tovary the location of the focal point in the direction of propagation ofthe electromagnetic radiation beam. The xy-scan device can be operableto vary the location of the focal point transverse to the direction ofpropagation of the electromagnetic radiation beam.

In many embodiments of the system, the free-floating mechanism includesbeam deflection devices. For example, the free-floating mechanism caninclude a first beam deflection device and a second beam deflectiondevice. The first beam deflection device can be configured to deflectthe electromagnetic radiation beam propagating in a first direction topropagate in a second direction different from the first direction. Thesecond beam deflection device can be configured to deflect theelectromagnetic radiation beam propagating in the second direction topropagate in a third direction different from the second direction. Thefirst beam deflection device can also be configured to deflect a portionof the electromagnetic radiation beam reflected from the focal pointlocation and propagating opposite to the third direction to propagateopposite to the second direction. The second beam deflection device canalso be configured to deflect a portion of the electromagnetic radiationbeam reflected from the focal point and propagating opposite to thesecond direction to propagate opposite to the first direction. At leastone of (1) a distance between the first and second beam deflectiondevices and (2) a rotational orientation between the first and secondbeam deflection devices can be varied to accommodate movement of theeye.

The free-floating mechanism can include a third beam deflection device.The third beam deflection device can be configured to deflect theelectromagnetic radiation beam propagating in the third direction topropagate in a fourth direction different from the third direction. Thethird beam deflection device can also be configured to deflect a portionof the electromagnetic radiation beam reflected from the focal pointlocation and propagating opposite to the fourth direction to propagateopposite to the third direction. At least one of (1) a distance betweenthe second and third beam deflection devices and (2) a rotationalorientation between the second and third beam deflection devices can bevaried to accommodate movement of the eye.

In many embodiments of the system, the detection assembly includes asensor configured to generate the intensity signal. The detectionassembly can include an aperture configured to block portions of theelectromagnetic radiation beam reflected from locations other than thefocal point from reaching the sensor.

In many embodiments, the system includes a polarization-sensitive deviceand a polarizing device. The polarization-sensitive device can bedisposed along an optical path of the electromagnetic radiation beambetween the beam source and the free-floating mechanism. Theelectromagnetic radiation beam can pass through thepolarization-sensitive device during propagation of the electromagneticradiation beam from the beam source to the free-floating device. Thepolarizing device can be used to modify polarization of at least one ofthe electromagnetic radiation beam and a portion of the electromagneticradiation beam reflected from the focal point location. Thepolarization-sensitive device can reflect a portion of theelectromagnetic radiation beam reflected from the focal point so as toincident upon a sensor configured to generate the intensity signal. Thepolarizing device can include, for example, a one-quarter wave plate.

In many embodiments of the system, the electromagnetic radiation beamcan be configured to so as to not modify tissue. For example, theelectromagnetic radiation beam can have an energy level below athreshold level that would modify tissue. Alternatively, theelectromagnetic radiation beam can be configured to modify tissue.

The electromagnetic radiation beam can have any suitable configuration.For example, the electromagnetic radiation beam can include a pluralityof laser pulses having a wavelength between 320 nanometers and 430nanometers. As another example, the electromagnetic radiation beam caninclude a plurality of laser pulses having a wavelength between 800nanometers and 1100 nanometers. As a further example, theelectromagnetic radiation beam can include a plurality of laser pulseshaving a pulse duration of between 100 femtoseconds and 15 nanoseconds.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the ensuing detailed descriptionand accompanying drawings. Other aspects, objects and advantages of theinvention will be apparent from the drawings and detailed descriptionthat follows.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference in their entirety tothe same extent as if each individual publication, patent, or patentapplication was specifically and individually indicated to beincorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a schematic diagram of a laser surgery system, in accordancewith many embodiments, in which a patient interface device is coupled toa laser assembly and a detection assembly by way of a scanning assemblyand free-floating mechanism that supports the scanning assembly.

FIG. 2 is a schematic diagram of an embodiment of the laser surgerysystem of FIG. 1.

FIG. 3A shows an isometric view of an embodiment of the free-floatingmechanism and scanning assembly of FIG. 1.

FIG. 3B schematically illustrates relative movements that can be used inembodiments of the free-floating mechanism and scanning assembly of FIG.1.

FIG. 4 is a simplified block diagrams of acts of a method, in accordancewith many embodiments, of imaging and/or modifying an intraoculartarget.

FIGS. 5, 6, and 7 are simplified block diagrams of optional acts, inaccordance with many embodiments, that can be accomplished in the methodof FIG. 4.

FIG. 8 is a schematic diagram of an embodiment of the laser surgerysystem of FIG. 1.

FIG. 9 is a plan view illustrating a calibration plate, in accordancewith many embodiments, that can be used to calibrate the laser surgerysystem of FIG. 1.

FIG. 10 is a schematic diagram illustrating using the calibration plateof FIG. 9 to calibrate a camera of the laser surgery system of FIG. 1.

FIG. 11 is a schematic diagram illustrating using the calibration plateof FIG. 9 to calibrate the scanning assembly of the laser surgery systemof FIG. 1.

FIG. 12 is a schematic diagram illustrating using a fluorescent materialto calibrate the scanning assembly of the laser surgery system of FIG.1.

FIG. 13 is a schematic diagram illustrating using a repositionablereflective surface to calibrate the scanning assembly of the lasersurgery system of FIG. 1.

FIG. 14 illustrates variation in intensity of a signal generated usingthe reflective surface of FIG. 13 relative to a control parameter for az-scan device of the laser surgery system of FIG. 1.

FIG. 15 shows a plan view of a capsulotomy incision locator and across-sectional view showing projection of the capsulotomy incisionlocator on the lens anterior capsule, in accordance with manyembodiments.

FIG. 16 shows a cross-sectional view of an eye and a capsulotomyincision region defining a closed boundary incision surface transectingthe lens anterior capsule, in accordance with many embodiments.

FIG. 17 is a simplified block diagram of acts of a method for adaptivelyscanning the focal point of the electromagnetic radiation beam relativeto a boundary of an intraocular target, in accordance with manyembodiments.

FIG. 18 illustrates variation in intensity of a signal generated whilescanning the focal point of the electromagnetic radiation beam in a scanpattern that crosses a boundary of an intraocular target, in accordancewith many embodiments.

FIG. 19 is a schematic diagram illustrating repeatedly using a locationof where a scan pattern for the focal point crosses a boundary of anintraocular target to determine upper and/or lower depth limits for asubsequent scan pattern for the focal point, in accordance with manyembodiments.

FIG. 20 is a schematic diagram illustrating a series of scan patternsthat can be used to incise a surface that transects a boundary of anintraocular target, in accordance with many embodiments.

FIG. 21 and FIG. 22 are schematic diagrams illustrating embodiments ofscanning directions that can be used with the scan patterns of FIG. 20.

FIGS. 23 through 25 illustrate aspects of arcuate incisions of a corneathat can be formed by the laser surgery system of FIG. 1, in accordancewith many embodiments.

FIGS. 26 through 31 illustrate aspects of primary cataract surgeryaccess incisions of a cornea that can be formed by the laser surgerysystem of FIG. 1, in accordance with many embodiments.

FIGS. 32 through 36 illustrate aspects of sideport cataract surgeryaccess incisions of a cornea that can be formed by the laser surgerysystem of FIG. 1, in accordance with many embodiments.

FIGS. 37 and 38 are simplified block diagrams of acts of methods forcontrolling the intensity of an electromagnetic radiation beam that canbe used in the laser surgery system of FIG. 1, in accordance with manyembodiments.

FIG. 39 is a side view diagram of an IOL positioned in a lens capsuleand an adjacent portion of the anterior hyaloid surface of the vitreous,in accordance with many embodiments.

FIG. 40 is a side view diagram showing the adjacent portion of theanterior hyaloids surface of the vitreous displaced relative to the IOLof FIG. 39 and a closed boundary incision surface transecting the lensposterior capsule that can be formed by the laser surgery system of FIG.1, in accordance with many embodiments.

FIG. 41 is a side view diagram showing refractive index changes that canbe induced in an IOL by the laser surgery system of FIG. 1, inaccordance with many embodiments.

FIG. 42 through FIG. 44 illustrate aspects of lens fragmentationincisions that can be formed by the laser surgery system of FIG. 1, inaccordance with many embodiments.

FIG. 45 illustrates lens fragmentation patterns, in accordance with manyembodiments.

FIG. 46 is a perspective view of a corneal flap that can be formed bythe laser surgery system of FIG. 1, in accordance with many embodiments.

FIG. 47 is a cross-sectional view of a cornea after the periphery andedge of the corneal flap of FIG. 46 have been incised by the lasersurgery system of FIG. 1.

FIG. 48 is a plan view of a cornea after the periphery and edge of thecorneal flap of FIG. 46 have been incised by the laser surgery system ofFIG. 1.

FIG. 49 is a cross-sectional view of a corneal flap of FIG. 46 shownpeeled back from the cornea.

FIG. 50 and FIG. 51 are cross-sectional views of a cornea illustratingexample intra-stromal incised volumes, in accordance with manyembodiments, that can be created by the laser surgery system of FIG. 1.

FIG. 52 and FIG. 53 are a cross-sectional view and a plan view of acornea, respectively, and illustrate a corneal intra-stromal pocket, inaccordance with many embodiments, that can be created by the lasersurgery system of FIG. 1.

FIG. 54 illustrates a configuration of a scanning assembly and anobjective lens assembly, in accordance with many embodiments of thelaser surgery system of FIG. 1, that are configured to providesubstantial clearance between the scanning assembly and the patientwithout using a lens relay and with a reduced diameter objective lensassembly.

FIG. 55 illustrates an objective lens assembly that utilizes a lensrelay and associated excessive clearance between the scanning assemblyand the patient.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. It will also, however, be apparent toone skilled in the art that the present invention can be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Systems for imaging and/or treating an eye of a patient are provided. Inmany embodiments, a free-floating mechanism provides a variable opticalpath by which a portion of an electromagnetic beam reflected from afocal point disposed within the eye is directed to a path lengthinsensitive imaging assembly, such as a confocal detection assembly. Inmany embodiments, the free-floating mechanism is configured toaccommodate movement of the patient while maintaining alignment betweenan electromagnetic radiation beam and the patient. The electromagneticradiation beam can be configured for imaging the eye, can be configuredfor treating the eye, and can be configured for imaging and treating theeye.

Referring now to the drawings in which like numbers reference similarelements, FIG. 1 schematically illustrates a laser surgery system 10, inaccordance with many embodiments. The laser surgery system 10 includes alaser assembly 12, a confocal detection assembly 14, a free-floatingmechanism 16, a scanning assembly 18, an objective lens assembly 20, anda patient interface device 22. The patient interface device 22 isconfigured to interface with a patient 24. The patient interface device22 is supported by the objective lens assembly 20. The objective lensassembly 20 is supported by the scanning assembly 18. The scanningassembly 18 is supported by the free-floating mechanism 16. Thefree-floating mechanism 16 has a portion having a fixed position andorientation relative to the laser assembly 12 and the confocal detectionassembly 14.

In many embodiments, the patient interface device 22 is configured tointerface with an eye of the patient 24. For example, the patientinterface device 22 can be configured to be vacuum coupled to an eye ofthe patient 24 such as described in U.S. Provisional Patent ApplicationSer. No. 61/721,693, entitled “Liquid Optical Interface for Laser EyeSurgery System”, filed Nov. 2, 2012. The laser surgery system 10 canfurther optionally include a base assembly 26 that can be fixed in placeor repositionable. For example, the base assembly 26 can be supported bya support linkage that is configured to allow selective repositioning ofthe base assembly 26 relative to a patient and secure the base assembly26 in a selected fixed position relative to the patient. Such a supportlinkage can be supported in any suitable manner such as, for example, bya fixed support base or by a movable cart that can be repositioned to asuitable location adjacent to a patient. In many embodiments, thesupport linkage includes setup joints with each setup joint beingconfigured to permit selective articulation of the setup joint and canbe selectively locked to prevent inadvertent articulation of the setupjoint, thereby securing the base assembly 26 in a selected fixedposition relative to the patient when the setup joints are locked.

In many embodiments, the laser assembly 12 is configured to emit anelectromagnetic radiation beam 28. The beam 28 can include a series oflaser pulses of any suitable energy level, duration, and repetitionrate.

In many embodiments, the laser assembly 12 incorporates femtosecond (FS)laser technology. By using femtosecond laser technology, a shortduration (e.g., approximately 10⁻¹³ seconds in duration) laser pulse(with energy level in the micro joule range) can be delivered to atightly focused point to disrupt tissue, thereby substantially loweringthe energy level required to image and/or modify an intraocular targetas compared to laser pulses having longer durations.

The laser assembly 12 can produce laser pulses having a wavelengthsuitable to treat and/or image tissue. For example, the laser assembly12 can be configured to emit an electromagnetic radiation beam 28 suchas emitted by any of the laser surgery systems described in copendingU.S. Provisional Patent Application Ser. No. 61/722,048, entitled “LaserEye Surgery System”, filed Nov. 2, 2012; and U.S. patent applicationSer. No. 12/987,069, entitled “Method and System For Modifying EyeTissue and Intraocular Lenses”, filed Jan. 7, 2011. For example, thelaser assembly 12 can produce laser pulses having a wavelength from 1020nm to 1050 nm. For example, the laser assembly 12 can have adiode-pumped solid-state configuration with a 1030 (+/−5) nm centerwavelength. As another example, the laser assembly 12 can produce laserpulses having a wavelength 320 nm to 430 nm. For example, the laserassembly 12 can include an Nd:YAG laser source operating at the 3rdharmonic wavelength (355 nm) and producing pulses having 50 pico secondto 15 nano second pulse duration. Depending on the spot size, typicalpulse energies used can be in the nano joule to micro joule range. Thelaser assembly 12 can also include two or more lasers of any suitableconfiguration.

The laser assembly 12 can include control and conditioning components.For example, such control components can include components such as abeam attenuator to control the energy of the laser pulse and the averagepower of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly and afixed optical relay to transfer the laser pulses over a distance whileaccommodating laser pulse beam positional and/or directionalvariability, thereby providing increased tolerance for componentvariation.

In many embodiments, the laser assembly 12 and the confocal detectionassembly 14 have fixed positions relative to the base assembly 26. Thebeam 28 emitted by the laser assembly 12 propagates along a fixedoptical path through the confocal detection assembly 14 to thefree-floating mechanism 16. The beam 28 propagates through thefree-floating mechanism 16 along a variable optical path 30, whichdelivers the beam 28 to the scanning assembly 18. In many embodiments,the beam 28 emitted by the laser assembly 12 is collimated so that thebeam 28 is not impacted by patient movement induced changes in thelength of the optical path between the laser assembly 12 and the scanner16. The scanning assembly 18 is operable to scan the beam 28 (e.g., viacontrolled variable deflection of the beam 28) in at least onedimension. In many embodiments, the scanning assembly 18 is operable toscan the beam 28 in two dimensions transverse to the direction ofpropagation of the beam 28 and is further operable to scan the locationof a focal point of the beam 28 in the direction of propagation of thebeam 28. The scanned beam is emitted from the scanning assembly 18 topropagate through the objective lens assembly 20, through the interfacedevice 22, and to the patient 24.

The free-floating mechanism 16 is configured to accommodate a range ofmovement of the patient 24 relative to the laser assembly 12 and theconfocal detection assembly 14 in one or more directions whilemaintaining alignment of the beam 28 emitted by the scanning assembly 18with the patient 24. For example, in many embodiments, the free-floatingmechanism 16 is configured to accommodate a range movement of thepatient 24 in any direction defined by any combination of unitorthogonal directions (X, Y, and Z).

The free-floating mechanism 16 supports the scanning assembly 18 andprovides the variable optical path 30, which changes in response tomovement of the patient 24. Because the patient interface device 22 isinterfaced with the patient 24, movement of the patient 24 results incorresponding movement of the patient interface device 22, the objectivelens assembly 20, and the scanning assembly 18. The free-floatingmechanism 16 can include, for example, any suitable combination of alinkage that accommodates relative movement between the scanningassembly 18 and, for example, the confocal detection assembly 24, andoptical components suitably tied to the linkage so as to form thevariable optical path 30.

A portion of the electromagnetic radiation beam 28 that is reflected byeye tissue at the focal point propagates back to the confocal detectionassembly 14. Specifically, a reflected portion of the electromagneticradiation beam 28 travels back through the patient interface device 22,back through the objective lens assembly 20, back through (andde-scanned by) the scanning assembly 18, back through the free-floatingmechanism 16 (along the variable optical path 30), and to the confocaldetection assembly 14. In many embodiments, the reflected portion of theelectromagnetic radiation beam that travels back to the confocaldetection assembly 14 is directed to be incident upon a sensor thatgenerates an intensity signal indicative of intensity of the incidentportion of the electromagnetic radiation beam. The intensity signal,coupled with associated scanning of the focal point within the eye, canbe processed in conjunction with the parameters of the scanning to, forexample, image/locate structures of the eye, such as the anteriorsurface of the cornea, the posterior surface of the cornea, the iris,the anterior surface of the lens capsule, and the posterior surface ofthe lens capsule. In many embodiments, the amount of the reflectedelectromagnetic radiation beam that travels to the confocal detectionassembly 14 is substantially independent of expected variations in thelength of the variable optical path 30 due to patient movement, therebyenabling the ability to ignore patient movements when processing theintensity signal to image/locate structures of the eye.

FIG. 2 schematically illustrates details of an embodiment of the lasersurgery system 10. Specifically, example configurations areschematically illustrated for the laser assembly 12, the confocaldetection assembly 14, and the scanning assembly 18. As shown in theillustrated embodiment, the laser assembly 12 can include an ultrafast(UF) laser 32 (e.g., a femtosecond laser), alignment mirrors 34, 36, abeam expander 38, a one-half wave plate 40, a polarizer and beam dumpdevice 42, output pickoffs and monitors 44, and a system-controlledshutter 46. The electromagnetic radiation beam 28 output by the laser 32is deflected by the alignment mirrors 34, 36. In many embodiments, thealignment mirrors 34, 36 are adjustable in position and/or orientationso as to provide the ability to align the beam 28 with the downstreamoptical path through the downstream optical components. Next, the beam28 passes through the beam expander 38, which increases the diameter ofthe beam 28. Next, the expanded beam 28 passes through the one-half waveplate 40 before passing through the polarizer. The beam exiting thelaser is linearly polarized. The one-half wave plate 40 can rotate thispolarization. The amount of light passing through the polarizer dependson the angle of the rotation of the linear polarization. Therefore, theone-half wave plate 40 with the polarizer acts as an attenuator of thebeam 28. The light rejected from this attenuation is directed into thebeam dump. Next, the attenuated beam 28 passes through the outputpickoffs and monitors 44 and then through the system-controlled shutter46. By locating the system-controlled shutter 46 downstream of theoutput pickoffs and monitors 44, the power of the beam 28 can be checkedbefore opening the system-controlled shutter 46.

As shown in the illustrated embodiment, the confocal detection assembly14 can include a polarization-sensitive device such as a polarized orunpolarized beam splitter 48, a filter 50, a focusing lens 51, a pinholeaperture 52, and a detection sensor 54. A one-quarter wave plate 56 isdisposed downstream of the polarized beam splitter 48. The beam 28 asreceived from the laser assembly 12 is polarized so as to pass throughthe polarized beam splitter 48. Next, the beam 28 passes through theone-quarter wave plate 56, thereby rotating the polarization axis of thebeam 28. A quarter rotation is a presently preferred rotation amount.After reflecting from the focal point in the eye, the returningreflected portion of the beam 28 passes back through the one-quarterwave plate 56, thereby further rotating the polarization axis of thereturning reflected portion of the beam 28. Ideally, after passing backthrough the one-quarter wave plate 56, the returning reflected portionof the beam has experienced a total polarization rotation of 90 degreesso that the reflected light from the eye is fully reflected by thepolarized beam splitter 48. The birefringence of the cornea can also betaken into account if, for example, the imaged structure is the lens. Insuch a case, the plate 56 can be adjusted/configured so that the doublepass of the plate 56 as well as the double pass of the cornea sum up toa polarization rotation of 90 degrees. Because the birefringence of thecornea may be different form patient to patient, theconfiguration/adjustment of the plate 56 can be done dynamically so asto optimize the signal returning to the detection sensor 54.Accordingly, the returning reflected portion of the beam 28 is nowpolarized to be at least partially reflected by the polarized beamsplitter 48 so as to be directed through the filter 50, through the lens51, and to the pinhole aperture 52. The filter 50 can be configured toblock wavelengths other than the wavelengths of interest. The pinholeaperture 52 is configured to block any returning reflected portion ofthe beam 28 reflected from locations other than the focal point fromreaching the detection sensor 54. Because the amount of returningreflected portion of the beam 28 that reaches the detection sensor 54depends upon the nature of the tissue at the focal point of the beam 28,the signal generated by the detection sensor 54 can be processed incombination with data regarding the associated locations of the focalpoint so as to generate image/location data for structures of the eye.

As shown in the illustrated embodiment, the scanning assembly 18 caninclude a z-scan device 58 and a xy-scan device 60. The z-scan device 58is operable to vary a convergence/divergence angle of the beam 28 andthereby change a location of the focal point in the direction ofpropagation of the beam 28. For example, the z-scan device 58 caninclude one or more lenses that are controllably movable in thedirection of propagation of the beam 28 to vary a convergence/divergenceangle of the beam 28. The xy-scan device 60 is operable to deflect thebeam 28 in two dimensions transverse to the direction of propagation ofthe beam 28. For example, the xy-scan device 60 can include one or moremirrors that are controllably deflectable to scan the beam 28 in twodimensions transverse to the direction of propagation of the beam 28.Accordingly, the combination of the z-scan device 58 and the xy-scandevice 60 can be operated to controllably scan the focal point in threedimensions, for example, within the eye of the patient.

As shown in the illustrated embodiment, a camera 62 and associated videoillumination 64 can be integrated with the scanning assembly 18. Thecamera 62 and the beam 28 share a common optical path through theobjective lens assembly 20 to the eye. A video dichroic 66 is used tocombine/separate the beam 28 with/from the illumination wavelengths usedby the camera. For example, the beam 28 can have a wavelength of about355 nm and the video illumination 64 can be configured to emitillumination having wavelengths greater than 450 nm. Accordingly, thevideo dichroic 66 can be configured to reflect the 355 nm wavelengthwhile transmitting wavelengths greater than 450 nm.

FIG. 3A shows an example embodiment of the free-floating mechanism 16(shown supporting a scanning assembly 18, an objective lens assembly 20,and a patient interface device 22) to illustrate a suitable linkage thataccommodates relative movement between the scanning assembly 18 and theconfocal detection assembly 14. Optical components are coupled withassociated links of the linkage so as to form the variable optical path30. The free-floating mechanism 16 includes a first support assembly 72,a second support assembly 74, and a base assembly 76. The eye interfacedevice 22 is coupled with and supported by the objective lens assembly20. The objective lens assembly 20 is coupled with and supported by thescanning assembly 18. The combination of the interface device 22, theobjective lens assembly 20, and the scanning assembly 18 form a unitthat moves in unison in response to movement of the patient.

The first support assembly 72 includes a first end frame 78, a secondend frame 80, and transverse rods 82, 84, which extend between andcouple to the end frames 78, 80. The transverse rods 82, 84 are orientedparallel to a first direction 86. The scanning assembly 18 is supportedby the transverse rods 82, 84 and slides along the rods 82, 84 inresponse to patient movement parallel to the first direction 86. Thetransverse rods 82, 84 form part of a linear bearing accommodatingpatient movement parallel to the first direction 86.

The second support assembly 74 includes a first end frame 88, anintermediate frame 90, transverse rods 92, 94, a second end frame 96,and vertical rods 98, 100. The transverse rods 92, 94 extend between andcouple to the first end frame 88 and to the intermediate frame 90. Thetransverse rods 92, 94 are oriented parallel to a second direction 102,which is at least transverse to and can be orthogonal to the firstdirection 86. Each of the first and second directions 86, 102 can behorizontal. The first support assembly 72 is supported by the transverserods 92, 94 and slides along the rods 92, 94 in response to patientmovement parallel to the second direction 102. The transverse rods 92,94 form part of a linear bearing accommodating patient movement parallelto the second direction 102. The vertical rods 98, 100 extend betweenand couple to the intermediate frame 90 and to the second end frame 96.The vertical rods 98, 100 are oriented parallel to a third direction104, which is at least transverse to each of first and second directions86, 102, and can be orthogonal to at least one of the first and seconddirections 86, 102. The vertical rods 98, 100 form part of a linearbearing accommodating relative movement between the second supportassembly 74 and the base assembly 76 parallel to the third direction104, thereby accommodating patient movement parallel to the thirddirection 104.

First, second, and third reflectors 106, 108, 110 (e.g., mirrors) aresupported by the free-floating mechanism 16 and configured to reflectthe electromagnetic radiation beam 28 to propagate along the variableoptical path 30. The first reflector 106 is mounted to the first supportassembly 72 (to the first end frame 78 in the illustrated embodiment).The second reflector 108 is mounted to the second support assembly 74(to the intermediate frame 90 in the illustrated embodiment). The thirdreflector 110 is mounted to the base assembly 76. In operation, the beam28 emitted by the laser assembly is deflected by the third reflector 110so as to propagate parallel to the third direction 104 and be incidentupon the second reflector 108. The second reflector 108 deflects thebeam 28 so as to propagate parallel to the second direction 102 and beincident upon the first reflector 106. The first reflector 106 deflectsthe beam 28 so as to propagate parallel to the first direction 86 andinto the scanning assembly 18, which then controllably scans and outputsthe scanned beam through the objective lens assembly 20 and the eyeinterface device 22. By propagating the beam 28 parallel to the thirddirection 104 from the third reflector 110 to the second reflector 108,the length of the corresponding portion of the variable optical path 30can be varied so as to accommodate relative movement of the patientrelative to the third direction 104. By propagating the beam 28 parallelto the second direction 102 from the second reflector 108 to the firstreflector 106, the length of the corresponding portion of the variableoptical path 30 can be varied so as to accommodate relative movement ofthe patient relative to the second direction 102. By propagating thebeam 28 parallel to the first direction 86 from the first reflector 106to the scanning assembly 18, the length of the corresponding portion ofthe variable optical path 30 can be varied so as to accommodate relativemovement of the patient relative to the first direction 86.

In the illustrated embodiment, the free-floating mechanism 16 furtherincludes a first solenoid brake assembly 112, a second solenoid brakeassembly 114, and a third solenoid brake assembly 116. The solenoidbrake assemblies 112, 114, 116 are operable to selectively preventinadvertent articulation of the free-floating mechanism 16 duringinitial positioning of the laser surgery system 10 relative to apatient's eye. Inadvertent articulation of the free-floating mechanism16 may occur, for example, when the laser surgery system 10 is initiallyrepositioned to be in a suitable position relative to the patient. Forexample, in the absence of any mechanism for preventing inadvertentarticulation of the free-floating mechanism 16, movement of the lasersurgery system 10 may induce inadvertent articulation of thefree-floating mechanism 16, especially when a user induces movement ofthe laser surgery system 10 through contact with, for example, theobjective lens assembly 20 to move the objective lens assembly 20 into asuitable location relative to the patient. When the laser surgery system10 is supported by a support linkage mechanism that includes setupjoints, preventing inadvertent articulation of the free-floatingmechanism 16 can be used to ensure that the initial positioning of thelaser surgery system occurs via articulation of the setup joints insteadof via articulation of the free-floating mechanism 16.

The first solenoid brake assembly 112 is configured to selectivelyprevent inadvertent movement between the scanning assembly 18 and thefirst support assembly 72. Engagement of the first solenoid brakeassembly 112 prevents movement of the scanning assembly 18 along thetransverse rods 82, 84, thereby preventing relative movement between thescanning assembly 18 and the first support assembly 72 parallel to thefirst direction 86. When the first solenoid brake assembly 112 is notengaged, the scanning assembly 18 is free to slide along the transverserods 82, 84, thereby permitting relative movement between the scanningassembly 18 and the first support assembly 72 parallel to the firstdirection 86. In many embodiments, the free-floating mechanism 16includes a detent mechanism and/or an indicator that is configured topermit engagement of the first solenoid brake assembly 112 when thescanning assembly 18 is centered relative to its range of travel alongthe transverse rods 82, 84, thereby ensuring equal range of travel ofthe scanning assembly 18 in both directions parallel to the firstdirection 86 when the first solenoid brake assembly 112 is disengagedfollowing positioning of the objective lens assembly 20 relative to thepatient.

The second solenoid brake assembly 114 is configured to selectivelyprevent inadvertent movement between the first support assembly 72 andthe second support assembly 74. Engagement of the second solenoid brakeassembly 114 prevents movement of the first support assembly 72 alongthe transverse rods 92, 94, thereby preventing relative movement betweenthe first support assembly 72 and the second support assembly 74parallel to the second direction 102. When the second solenoid brakeassembly 114 is not engaged, the first support assembly 72 is free toslide along the transverse rods 92, 94, thereby permitting relativemovement between the first support assembly 72 and the second supportassembly 74 parallel to the second direction 102. In many embodiments,the free-floating mechanism 16 includes a detent mechanism and/or anindicator that is configured to permit engagement of the second solenoidbrake assembly 114 when the first support assembly 72 is centeredrelative to its range of travel along the transverse rods 92, 94,thereby ensuring equal range of travel of the first support assembly 72in both directions parallel to the second direction 102 when the secondsolenoid brake assembly 114 is disengaged following positioning of theobjective lens assembly 20 relative to the patient.

The third solenoid brake assembly 116 is configured to selectivelyprevent inadvertent movement between the second support assembly 74 andthe base assembly 76. Engagement of the third solenoid brake assembly116 prevents movement of the base assembly 76 along the vertical rods98, 100, thereby preventing relative movement between the second supportassembly 74 and the base assembly 76 parallel to the third direction104. When the third solenoid brake assembly 116 is not engaged, the baseassembly 76 is free to slide along the vertical rods 98, 100, therebypermitting relative movement between the second support assembly 74 andthe base assembly 76 parallel to the third direction 104. In manyembodiments, the free-floating mechanism 16 includes a detent mechanismand/or an indicator that is configured to permit engagement of the thirdsolenoid brake assembly 116 when the base assembly 76 is centeredrelative to its range of travel along the vertical rods 98, 100, therebyensuring equal range of travel of the base assembly 72 in bothdirections parallel to the third direction 102 when the third solenoidbrake assembly 116 is disengaged following positioning of the objectivelens assembly 20 relative to the patient.

In an optional embodiment, the third reflector 110 is omitted and theincoming beam 28 is directed to propagate parallel to the thirddirection 104 so as to be incident on the second reflector 108. Each ofthe reflectors 106, 108, 110 can be adjustable in position and/or inorientation and thereby can be adjusted to align the correspondingportions of the variable optical path 30 with the first, second, andthird directions 86, 102, 104, respectively. Accordingly, the use of thethird reflector 110 can provide the ability to align the portion of thevariable optical path 30 between the third reflector 110 and the secondreflector 108 so as to be parallel to the third direction 104 andthereby compensate for relative positional and/or orientationvariability between the laser assembly 12 and the free-floatingmechanism 16.

In the illustrated embodiment of the free-floating mechanism 16, thefirst and second directions 86, 102 can be horizontal and the thirddirection 104 can be vertical. The free-floating mechanism 16 can alsoinclude a counter-balance mechanism configured to inhibitgravity-induced movement of the eye interface device 22 and/or transferof gravity-induced force to an eye via the eye interface device 22. Forexample, a counter-balance mechanism can be employed to apply acounter-balancing vertical force to the second assembly 74, therebyinhibiting or even preventing gravity-induced relative movement betweenthe second assembly 74 and the base assembly 76 and/or transfer ofgravity-induced force to an eye via the eye interface device 22.

Other suitable variations of the free-floating mechanism 16 arepossible. For example, the scanning assembly 18 can be slidablysupported relative to a first support assembly via a vertically-orientedlinear bearing. The first support assembly can be slidably supportedrelative to a second support assembly via a first horizontally-orientedlinear bearing. The second support assembly can be slidably supportedrelative to a base assembly via a second horizontally-oriented linearbearing that is oriented transverse (e.g., perpendicular) to the firsthorizontally-oriented linear bearing. In such a configuration, acounter-balancing mechanism can be used to apply a counter-balancingforce to the scanning assembly 18, thereby inhibiting or even preventinggravity-induced movement of the scanning assembly 18 and the eyeinterface device 22 and/or transfer of gravity-induced force to an eyecoupled with the eye interface device 22. The free-floating mechanism 16can also incorporate one or more sensors configured to monitor relativeposition (1) between the scanning assembly 18 and the first supportassembly 72, (2) between the first support assembly 72 and the secondsupport assembly 74, and/or (3) between the second support assembly 74and the base assembly 76.

FIG. 3B schematically illustrates relative movements that can be used inthe free-floating mechanism 16 that can be used to accommodate patientmovement, in accordance with many embodiments. The free-floatingmechanism 16 includes the first reflector 106, the second reflector 108,and the third reflector 110. In many embodiments, the free-floatingmechanism 16 includes a linkage assembly (not shown) that is configuredto permit certain relative movement between the scanner 18 and the firstreflector 106, between the first reflector 106 and the second reflector108, and between the second reflector 108 and the third reflector 110 soas to consistently direct the electromagnetic radiation beam 28 to thescanner 18 while accommodating three-dimensional relative movementbetween the patient interface device 22 and the laser assemblygenerating the electromagnetic radiation beam 28. For example, similarto the embodiment of the free-floating mechanism 16 illustrated in FIG.3A, a free-floating mechanism 16 can be configured such that the scanner18 is supported by a first support assembly such that the scanner isfree to translate relative to the first support assembly parallel to thefirst direction 86, thereby maintaining the location and orientation ofthe beam 28 between the first reflector 106 and the scanner 18.Likewise, the first support assembly can be supported by a secondsupport assembly such that the first support assembly is free totranslate relative to the second support assembly parallel to a seconddirection 102, thereby maintaining the location and orientation of thebeam 28 between the second reflector 108 and the first reflector 106.And the second support assembly can be supported by a base assembly suchthat the second support assembly is free to translate relative to thebase assembly parallel to a third direction 104, thereby maintaining thelocation and orientation of the beam 28 between the third reflector 110and the second reflector 108.

The free-floating mechanism 16 can also employ one or more relativerotations so as to maintain the location and orientation of pathsegments of the beam 28. For example, the scanner 18 can be supported bya first support assembly such that the scanner is free to undergo arotation 118 relative to the first support assembly about an axiscoincident with the path segment of the beam 28 between the firstreflector 106 and the scanner 18, thereby maintaining the location andorientation of the beam 28 between the first reflector 106 and thescanner 18. Likewise, the first support assembly can be supported by asecond support assembly such that the first support assembly is free toundergo a rotation 120 relative to the second support assembly about anaxis coincident with the path segment of the beam 28 between the secondreflector 108 and the first reflector 106, thereby maintaining thelocation and orientation of the beam 28 between the second reflector 108and the first reflector 106. And the second support assembly can besupported by a base assembly such that the second support assembly isfree to undergo a rotation 122 relative to the base assembly about anaxis coincident with the path segment of the beam 28 between the thirdreflector 110 and the second reflector 108, thereby maintaining thelocation and orientation of the beam 28 between the third reflector 110and the second reflector 108.

The free-floating mechanism 16 can also employ any suitable combinationof relative translations and relative rotations so as to maintain thelocation and orientation of path segments of the beam 28. For example,with respect to the configuration illustrated in FIG. 3B, thefree-floating mechanism 16 can employ relative translation parallel tothe second direction 102, relative translation parallel to the thirddirection 104, and relative rotation 122, thereby allowingthree-dimensional movement of the patient interface 22 relative to thelaser assembly used to generate the beam 28, and thereby accommodatingpatient movement.

FIG. 4 is a simplified block diagram of acts of a method 200, inaccordance with many embodiments, of imaging an eye while accommodatingpatient movement. Any suitable device, assembly, and/or system, such asdescribed herein, can be used to practice the method 200. The method 200includes using a beam source to generate an electromagnetic radiationbeam (act 202).

The method 200 includes propagating the electromagnetic radiation beamfrom the beam source to a scanner along a variable optical path havingan optical path length that changes in response to movement of the eye(act 204). The method 200 includes focusing the electromagneticradiation beam to a focal point at a location within the eye (act 206).The method 200 includes using the scanner to scan the focal point todifferent locations within the eye (act 208). The method 200 includespropagating a portion of the electromagnetic radiation beam reflectedfrom the focal point location back along the variable optical path to asensor (act 210). The method 200 includes using the sensor to generatean intensity signal indicative of the intensity of a portion of theelectromagnetic radiation beam reflected from the focal point locationand propagated to the sensor (act 212).

FIGS. 5, 6 and 7 are simplified block diagrams of optional acts that canbe accomplished as part of the method 200. For example, the method 200can include using a first support assembly to support the scanner so asto accommodate relative movement between the scanner and the firstsupport assembly so as to accommodate movement of the eye (act 214). Themethod 200 can include using a second support assembly to support thefirst support assembly so as to accommodate relative movement betweenthe first support assembly and the second support assembly so as toaccommodate movement of the eye (act 216). The method 200 can includeusing the first support assembly to support a first reflector configuredto reflect the electromagnetic radiation beam so as to propagate to thescanner along a portion of the variable optical path (act 218). Themethod 200 can include using a base assembly to support the secondsupport assembly so as to accommodate relative movement between thesecond support assembly and the base assembly so as to accommodatemovement of the eye (act 220). The method 200 can include using thesecond support assembly to support a second reflector configured toreflect the electromagnetic radiation beam to propagate along a portionof the variable optical path so as to be incident on the first reflector(act 222). The method 200 can include using the sensor to generate theintensity signal comprises passing a reflected portion of theelectromagnetic radiation beam through an aperture to block portions ofthe electromagnetic radiation beam reflected from locations other thanthe focal point location (act 224). The method 200 can include passingthe electromagnetic radiation beam through a polarization-sensitivedevice (act 226). The method 200 can include modifying polarization ofat least one of the electromagnetic radiation beam and a portion of theelectromagnetic radiation beam reflected from the focal point location(act 228). The method 200 can include using the polarization-sensitivedevice to reflect a portion of the electromagnetic radiation beamreflected from the focal point location so as to be incident upon thesensor (act 230).

FIG. 8 schematically illustrates a laser surgery system 300, inaccordance with many embodiments. The laser surgery system 300 includesthe laser assembly 12, the confocal detection assembly 14, thefree-floating mechanism 16, the scanning assembly 18, the objective lensassembly 20, the patient interface 22, communication paths 302, controlelectronics 304, control panel/graphical user interface (GUI) 306, anduser interface devices 308. The control electronics 304 includesprocessor 310, which includes memory 312. The patient interface 22 isconfigured to interface with a patient 24. The control electronics 304is operatively coupled via the communication paths 302 with the laserassembly 12, the confocal detection assembly 14, the free-floatingmechanism 16, the scanning assembly 18, the control panel/GUI 306, andthe user interface devices 308.

The free-floating mechanism 16 can be configured as illustrated in FIG.3 to include, for example, the first reflector 106, the second reflector108, and the third reflector 110. Accordingly, the free-floatingmechanism 16 can be configured to accommodate movement of the patient 24relative to the laser assembly 12 and the confocal detection assembly 14in any direction resulting from any combination of three orthogonal unitdirections.

The scanning assembly 18 can include a z-scan device and a xy-scandevice. The laser surgery system 300 can be configured to focus theelectromagnetic radiation beam 28 to a focal point that is scanned inthree dimensions. The z-scan device can be operable to vary the locationof the focal point in the direction of propagation of the beam 28. Thexy-scan device can be operable to scan the location of the focal pointin two dimensions transverse to the direction of propagation of the beam28. Accordingly, the combination of the z-scan device and the xy-scandevice can be operated to controllably scan the focal point of the beamin three dimensions, including within a tissue of the patient 24 such aswithin an eye tissue of the patient 24. As illustrated above anddescribed with respect to FIG. 3, the scanning assembly 18 is supportedby the free-floating mechanism 16, which accommodates patient movementinduced movement of the scanning assembly 18 relative to the laserassembly 12 and the confocal detection assembly 14 in three dimensions.

The patient interface 22 is coupled to the patient 24 such that thepatient interface 22, the objective lens assembly 20, and the scanningassembly 18 move in conjunction with the patient 24. For example, inmany embodiments, the patient interface 22 employs a suction ring thatis vacuum attached to an eye of the patient 24. The suction ring can becoupled with the patient interface 22, for example, using vacuum tosecure the suction ring to the patient interface 22.

The control electronics 304 controls the operation of and/or can receiveinput from the laser assembly 12, the confocal detection assembly 14,the free-floating assembly 16, the scanning assembly 18, the patientinterface 22, the control panel/GUI 306, and the user interface devices308 via the communication paths 302. The communication paths 302 can beimplemented in any suitable configuration, including any suitable sharedor dedicated communication paths between the control electronics 304 andthe respective system components.

The control electronics 304 can include any suitable components, such asone or more processor, one or more field-programmable gate array (FPGA),and one or more memory storage devices. In many embodiments, the controlelectronics 304 controls the control panel/GUI 306 to provide forpre-procedure planning according to user specified treatment parametersas well as to provide user control over the laser eye surgery procedure.

The control electronics 304 can include a processor/controller 310 thatis used to perform calculations related to system operation and providecontrol signals to the various system elements. A computer readablemedium 312 is coupled to the processor 310 in order to store data usedby the processor and other system elements. The processor 310 interactswith the other components of the system as described more fullythroughout the present specification. In an embodiment, the memory 312can include a look up table that can be utilized to control one or morecomponents of the laser system surgery system 300.

The processor 310 can be a general purpose microprocessor configured toexecute instructions and data, such as a Pentium processor manufacturedby the Intel Corporation of Santa Clara, Calif. It can also be anApplication Specific Integrated Circuit (ASIC) that embodies at leastpart of the instructions for performing the method in accordance withthe embodiments of the present disclosure in software, firmware and/orhardware. As an example, such processors include dedicated circuitry,ASICs, combinatorial logic, other programmable processors, combinationsthereof, and the like.

The memory 312 can be local or distributed as appropriate to theparticular application. Memory 312 can include a number of memoriesincluding a main random access memory (RAM) for storage of instructionsand data during program execution and a read only memory (ROM) in whichfixed instructions are stored. Thus, the memory 312 provides persistent(non-volatile) storage for program and data files, and may include ahard disk drive, flash memory, a floppy disk drive along with associatedremovable media, a Compact Disk Read Only Memory (CD-ROM) drive, anoptical drive, removable media cartridges, and other like storage media.

The user interface devices 308 can include any suitable user inputdevice suitable to provide user input to the control electronics 304.For example, the user interface devices 308 can include devices such as,for example, a touch-screen display/input device, a keyboard, afootswitch, a keypad, a patient interface radio frequency identification(RFID) reader, an emergency stop button, and a key switch.

System Calibration

The laser surgery system 10 can be calibrated to relate locations in atreatment space with pixels in the camera 62 and with control parametersused to control the scanning assembly 18 such that the focal point ofthe electromagnetic radiation beam can be accurately positioned withinthe intraocular target. Such calibration can be accomplished at anysuitable time, for example, prior to using the laser surgery system 10to treat a patient's eye.

FIG. 9 is a top view diagram of a calibration plate 402 that can be usedto calibrate the laser surgery system 10. In many embodiments, thecalibration plate 402 is a thin plate having an array of targetfeatures, for example, through holes 404 therein. In alternateembodiments, the calibration plate 402 is a thin plate having a field ofsmall dots as the target features. While any suitable arrangement of thetarget features can be used, the calibration plate 402 of FIG. 9 has anorthogonal array of through holes 404. Any suitable number of the targetfeatures can be included in the calibration plate 402. For example, theillustrated embodiment has 29 rows and 29 columns of the through holes404, with three through holes at each of the four corners of thecalibration plate 402 being omitted from the orthogonal array of throughholes 404.

In many embodiments, each of the through holes 404 is sized small enoughto block a suitable portion of an electromagnetic radiation beam whenthe focal point of the electromagnetic radiation beam is not located atthe through hole. For example, each of the through holes 404 can have adiameter slightly greater than the diameter of the focal point of theelectromagnetic radiation beam so as to not block any of theelectromagnetic radiation beam when the focal point is positioned at oneof the through holes 404. In the embodiment shown, the through holes 404have a diameter of 5 μm, which is sized to be used in conjunction with afocal point diameter of 1 μm.

FIG. 10 schematically illustrates using the calibration plate 402 tocalibrate the camera 62 of the laser surgery system 10. The calibrationplate 402 is supported at a known fixed location relative to theobjective lens assembly 20. In many embodiments, the objective lensassembly 20 is configured for telecentric scanning of theelectromagnetic radiation beam and the calibration plate 402 issupported to be perpendicular to the direction of propagation of theelectromagnetic radiation beam. The calibration plate 402 is disposedbetween the objective lens assembly 20 and a light source 406. The lightsource 406 is used to illuminate the calibration plate 402. A portion ofthe illumination light from the light source 406 passes through each ofthe through holes 404, thereby producing an illuminated location withinthe field of view of the camera 62 at each of the through holes 404. Alight beam 408 from each of the through holes 404 passes through theobjective lens assembly 20, through the video dichroic 66, an into thecamera 62. In many embodiments, the camera 62 includes a sensor havingan orthogonal array of pixels (e.g., in x and y directions where thecorresponding z direction is in the direction of propagation of theelectromagnetic radiation beam). In many embodiments, X and Y pixelvalues for each of the light beams 408 is used in conjunction with theknown locations of the through holes 404 relative to the objective lensassembly 20 to determine the relationship between the camera X and Ypixel values and locations in the treatment space for dimensionstransverse to the propagation direction of the electromagnetic radiationbeam.

FIG. 11 schematically illustrates using the calibration plate 402 tocalibrate the scanning assembly 18. The calibration plate 402 issupported at a known fixed location relative to the objective lensassembly 20. In many embodiments, the objective lens assembly 20 isconfigured for telecentric scanning of the electromagnetic radiationbeam and the calibration plate 402 is supported to be perpendicular tothe direction of propagation of the electromagnetic radiation beam. Thecalibration plate 402 is disposed between the objective lens assembly 20and a detector 410. The detector 410 is configured to generate a signalindicative of how much of the electromagnetic radiation beam is incidentthereon, thereby being indirectly indicative of how much of theelectromagnetic radiation beam is blocked by the calibration plate 402.For example, when the focal point of the electromagnetic radiation beamis positioned at one of the through holes 404 (as illustrated for thefocal point disposed on the right side of the detection plate 402 inFIG. 11), a maximum amount of the electromagnetic radiation beam passesthrough the through hole and is incident on the detector 410. Incontrast, when the focal point of the electromagnetic radiation beam isnot positioned at one of the through holes 404 (as illustrated for thefocal point disposed above the left side of the detection plate 402 inFIG. 11), a portion of the electromagnetic radiation beam is blockedfrom reaching the detector 410.

Control parameters for the z-scan device 58 and the xy-scan device 60are varied to locate the focal point of the electromagnetic radiationbeam at each of a suitable set of the through holes, thereby providingdata used to determine the relationship between the control parametersfor the scanning assembly 18 and the resulting location of the focalpoint of the electromagnetic radiation beam. The z-scan device 58 isoperable to vary a convergence/divergence angle of the electromagneticradiation beam, thereby being operable to control the distance of thefocal point from the objective lens in the direction of propagation ofthe electromagnetic radiation beam. The xy-scan device 60 is operable tovary a direction of the electromagnetic radiation beam in twodimensions, thereby providing the ability to move the focal point in twodimensions transverse to the direction of propagation of theelectromagnetic radiation beam.

A suitable existing search algorithm can be employed to vary the controlparameters for the z-scan device 58 and the xy-scan device 60 so as toreposition the focal point to be located at each of a suitable set ofthe through holes 404. In many embodiments where the objective lensassembly 20 is configured to telecentrically scan the electromagneticradiation beam, the resulting control parameter data for the scanningassembly 18 can be used to calibrate the scanning assembly 18 relativeto directions transverse to the direction of propagation of theelectromagnetic radiation beam (e.g., x and y directions transverse to az direction of propagation of the electromagnetic radiation beam).

FIG. 12 schematically illustrates using a fluorescent material block 412to calibrate the scanning assembly 18. The fluorescent material block412 is made of a suitable fluorescent material that emits light inresponse to absorbing electromagnetic radiation. The fluorescentmaterial block 412 is supported at a fixed location relative to theobjective lens assembly 20. With the focal point of the electromagneticradiation beam disposed within the block 412, the camera 62 is used toobserve the location of the resulting fluorescent emission in the block412. The observed location of the resulting fluorescent emission can beused in conjunction with calibration data for the camera 62 to determinex and y coordinates of the associated focal point in the treatmentspace. Suitable variation in the location of the focal point within thefluorescent material block 412 and associated position data for theresulting fluorescent emissions generated via the camera 62 can be usedto calibrate the control parameters for the scanning assembly 18. Forexample, in embodiments where the objective lens assembly 20 isconfigured to telecentrically scan the focal point, the correspondingpositional data for the resulting fluorescent emissions can be used togenerate calibrated control parameters for the xy-scan device 60 forpositioning the focal point transverse to the direction of propagationof the electromagnetic radiation beam.

FIG. 13 schematically illustrates the use of a reflective member 414 tocalibrate the scanning assembly 18. The reflective member 414 issupported at a suitable plurality of known fixed distances relative tothe objective lens assembly 20. In many embodiments, the objective lensassembly 20 is configured for telecentric scanning of theelectromagnetic radiation beam and the reflective member 414 issupported to be perpendicular to the direction of propagation of theelectromagnetic radiation beam. The reflective member 414 reflects theelectromagnetic radiation beam back through the objective lens assembly20, back through the scanning assembly 18, back through thefree-floating mechanism 16, and back to the confocal detection assembly14. For a particular distance between the objective lens assembly 20 andthe reflective member 414, the z-scan device 58 can be operated to varythe distance of the focal point from objective lens assembly.Alternatively, for a particular setting of the z-scan device resultingin a particular distance of the focal point from the objective lensassembly, the distance between the objective lens assembly 20 and thereflective member 414 can be varied. As illustrated in FIG. 14, aresulting signal 416 produced by the detection sensor 54 of the confocaldetection assembly 14 varies in intensity with variation in the distancebetween the focal point and the reflective member 414. The intensity ofthe signal 416 generated by the detection sensor 54 is maximized whenthe focal point is located at the surface of the reflective member 414,thereby maximizing the amount of reflected light that passes through thepinhole aperture 52 to reach the detection sensor 54. By determining thevalues of the control parameter for the z-scan device 58 correspondingto a suitable plurality of distances between the reflective member 414and the objective lens assembly 20, suitable calibration parameters canbe generated for use in controlling the z-scan device 58 to control thelocation of the focal point in the treatment space in the direction ofpropagation of the electromagnetic radiation beam.

Focal Point Scan Control

The laser surgery system 10 can be configured to image and/or modify anintraocular target by scanning the focal point of the electromagneticradiation beam in a particular area. For example, referring now to FIG.15 and FIG. 16, the laser surgery system 10 can be used to incise ananterior capsulotomy and/or a posterior capsulotomy in the anteriorportion of a lens capsule 418. The focal point of the electromagneticradiation beam can be scanned to form an anterior capsulotomy closedincision boundary surface 420 that transects the anterior portion of thelens capsule 418. Likewise, the focal point of the electromagneticradiation beam can be scanned to form a posterior capsulotomy closedincision boundary surface 430 that transects the posterior portion ofthe lens capsule 418.

The anterior and/or posterior closed incision boundary surfaces 420, 430can be designated using any suitable approach. For example, a plan viewof the patient's eye can be obtained using the camera 62. A capsulotomyincision designator 422 can be located and shown superimposed on theplan view of the patient's eye to illustrate the size, location, andshape of a planned capsulotomy relative to the patient's eye. Thecapsulotomy incision designator 422 can be manually defined by anoperator of the laser surgery system 10 and/or the laser surgery system10 can be configured to generate an initial capsulotomy incisiondesignator 422 for operator verification and/or modification.

The anterior capsulotomy closed incision boundary surface 420 can bedefined on a projection of the capsulotomy incision designator 422 suchthat the anterior capsulotomy closed incision boundary surface 420transects the anterior portion of the lens capsule 418 at all locationsaround the anterior capsulotomy incision boundary surface 420 for allexpected variations in the location of the anterior portion of the lenscapsule 418 relative to the projection of the capsulotomy incisiondesignator 422. For example, a curve corresponding to the capsulotomyincision designator 422 can be projected to define an intersection witha minimum depth mathematical surface model (e.g., a spherical surface)defining a minimum expected depth configuration for the anterior portionof the lens capsule 418 with the resulting intersection being ananterior capsulotomy upper closed curve 424 that defines an upperboundary for the anterior capsulotomy closed incision boundary surface420. Likewise, the curve corresponding to the capsulotomy incisiondesignator 422 can be projected to define an intersection with a maximumdepth mathematical surface model (e.g., a spherical surface) defining amaximum expected depth configuration for the anterior portion of thelens capsule 418 with the resulting intersection being an anteriorcapsulotomy lower closed curve 426 that defines a lower boundary for theanterior capsulotomy closed incision boundary surface 420.Alternatively, the focal point can be scanned using a low imaging-onlypower level (e.g., a power level sufficient to provide for imaging ofthe intraocular target via processing of the signal generated by thedetection sensor 54 of the confocal detection assembly 14 withoutmodifying the intraocular target) along the projection of thecapsulotomy incision designator 422 while varying the depth of the focalpoint to determine the depth of the anterior lens capsule at asufficient number of locations around the projection of the capsulotomyincision designator 422. For example, FIG. 18 illustrates variation ofintensity of the signal generated by the detection sensor 54 withvariation in depth of the focal point with the maximum peak in intensitycorresponding to the depth of the anterior portion of the lens capsule418. The measured depths of the anterior lens capsule can then be usedto determine suitable anterior capsulotomy upper and lower boundarycurves 424, 426 of the anterior capsulotomy closed incision boundarysurface 420.

In a similar fashion, the posterior capsulotomy closed incision boundarysurface 430 can be defined on a projection of the capsulotomy incisiondesignator 422 such that the posterior capsulotomy closed incisionboundary surface 430 transects the posterior portion of the lens capsule418 at all locations around the posterior capsulotomy incision boundarysurface 430 for all expected variations in the location of the posteriorportion of the lens capsule 418 relative to the projection of thecapsulotomy incision designator 422. For example, the curvecorresponding to the capsulotomy incision designator 422 can beprojected to define an intersection with a minimum depth mathematicalsurface model (e.g., a spherical surface) defining a minimum expecteddepth configuration for the posterior portion of the lens capsule 418with the resulting intersection being a posterior capsulotomy upperclosed curve 434 that defines an upper boundary for the posteriorcapsulotomy closed incision boundary surface 430. Likewise, the curvecorresponding to the capsulotomy incision designator 422 can beprojected to define an intersection with a maximum depth mathematicalsurface model (e.g., a spherical surface) defining a maximum expecteddepth configuration for the posterior portion of the lens capsule 418with the resulting intersection being a posterior capsulotomy lowerclosed curve 436 that defines a lower boundary for the posteriorcapsulotomy closed incision boundary surface 430. Alternatively, thefocal point can be scanned using a low imaging-only power level (e.g., apower level sufficient to provide for imaging of the intraocular targetvia processing of the signal generated by the detection sensor 54 of theconfocal detection assembly 14 without modifying the intraocular target)along the projection of the capsulotomy incision designator 422 whilevarying the depth of the focal point to determine the depth of theposterior lens capsule at a sufficient number of locations around theprojection of the capsulotomy incision designator 422. The measureddepths of the posterior lens capsule can then be used to determinesuitable posterior capsulotomy upper and lower boundary curves 434, 436of the posterior capsulotomy closed incision boundary surface 430.

While any suitable projection of the capsulotomy incision designator 422can be used to define the anterior and/or posterior capsulotomy incisionboundary surfaces 420, 430, in many embodiments an inverted cone shapedprojection of the capsulotomy incision designator 422 is employed so asto maintain a suitable safety margin distance between theelectromagnetic radiation beam, which converges to the focal point whilepropagating from the objective lens assembly 20 to the focal point, andthe edge of the iris. Accordingly, in many embodiments, the posteriorcapsulotomy has a smaller diameter than a corresponding anteriorcapsulotomy for a given capsulotomy incision designator 422, forexample, as illustrated.

The laser surgery system 10 can be used to form any suitably shapedcapsulotomy. For example, while the anterior and posterior capsulotomiesin the illustrated embodiments are circular, any other suitable shape,including but not limited to, elliptical, rectangular, and polygonal canbe formed. And the anterior and/or posterior capsulotomy can be shapedto accommodate any correspondingly suitably shaped IOL.

Concurrent Imaging and Adaptive Tissue Treatment

The laser surgery system 10 can be configured to generate image dataconcurrent with tissue treatment. For example, the focal point of theelectromagnetic radiation beam can have an intensity sufficient tomodify an intraocular target (e.g., eye tissue, an IOL) with a resultingportion of the electromagnetic radiation beam reflected from the focalpoint back to the detection sensor 54 of confocal detection assembly 14used to generate a signal that is processed to generate image datacorresponding to the focal point location.

By scanning the focal point in a pattern that crosses a boundary of anintraocular target, the detection sensor 54 can be used to concurrentlygenerate a signal that can be processed to identify the location of thecrossed boundary. For example, FIG. 18 illustrates variation ofintensity of the signal generated by the detection sensor 54 withvariation in depth of the focal point with the maximum peak in intensitycorresponding to the depth of the anterior portion of the lens capsule418. The location of the crossed boundary can be used to controlsubsequent scanning of the focal point so as to reduce the amount oftissue that is treated. For example, when incising an anteriorcapsulotomy in the lens capsule, the focal point can be scanned in ascan pattern that is at least in part based on the location of theanterior portion of the lens capsule as determined by processing thesignal from the detection sensor 54 generated during a previous scanpattern.

FIG. 17 is a simplified block diagram of acts of a method 500 foradaptively scanning the focal point of the electronic radiation beamrelative to a boundary of an intraocular target, in accordance with manyembodiments. The method 500 can be accomplished, for example, using anysuitable system including any suitable laser surgery system describedherein such as the laser surgery system 10.

The method 500 includes scanning a focal point of the electromagneticradiation beam in a first scan pattern so as to cross a boundary of anintraocular target (act 502). In many embodiments, the scan patternmoves the focal point transverse to and/or parallel to the direction ofpropagation of the electromagnetic radiation beam. The intraoculartarget having the crossed boundary can be any suitable intraoculartarget including, for example, the anterior lens capsule, the posteriorlens capsule, the crystalline lens, the cornea, the iris, an intraocularlens, and the limbus. Where a plurality of scan patterns is applied tocreate an incision surface (e.g., the closed incision boundary surface420 shown in FIGS. 15 and 16), the scan patterns can be configured suchthat the electromagnetic radiation beam propagates to the focal pointthrough unmodified eye tissue and/or IOL material. For example, the scanpatterns can be configured and accomplished such that modificationoccurs in a generally deeper to shallower manner.

The method 500 further includes generating a signal indicative of theintensity of a portion of the electromagnetic radiation beam reflectedfrom the focal point during the scanning of the focal point in the firstscan pattern (act 504). For example, because the first scan patterncrosses the boundary of the intraocular target, the signal generated bythe detection sensor (e.g., such as the signal illustrated in FIG. 18)and focal point position data for the first scan pattern can beprocessed to determine the location of the crossed boundary (act 506)by, for example, identifying a signal variation consistent with theapplicable boundary.

Having determined the location of where the first scan pattern crossedthe boundary of the intraocular target, the focal point can be scannedin a second scan pattern that is configured at least in part based onthe location where the first scan pattern crossed the boundary of theintraocular target (act 508). For example, the second scan pattern canbe configured to only extend beyond an estimated location of where thesecond scan pattern will cross the boundary of the intraocular target bypredetermined amounts selected to account for possible variations in theestimated location of where the second scan pattern will cross theboundary in view of knowing where the first scan pattern crossed theboundary of the intraocular target. In many embodiments, the second scanpattern will be immediately adjacent to if not overlapped with the firstscan pattern, thereby reducing the possible variation between themeasured location where the first scan pattern crossed the boundary andthe estimated location where the second scan pattern will cross theboundary. In many embodiments in which an incision surface is created, aseries of subsequent scan patterns can be accomplished in which thelocation where one or more previous scan patterns crossed the boundaryof the intraocular lens can be used to configured at least one of thesubsequent scan patterns to, for example, minimize the tissue and/ormaterial modified and/or increase the accuracy with regard to whichtissue and/or material is modified.

FIG. 19 schematically illustrates repeated use of a location where ascan pattern for the focal point crossed a boundary of an intraoculartarget to configure a subsequent scan pattern. While FIG. 19 employsscan patterns having variation in the location of the focal pointrelative to the z-dimension (i.e., parallel to the direction ofpropagation of the electromagnetic radiation beam), the conceptillustrated can be adapted to apply to any suitable scan pattern having,for example, variation in the location of the focal point relative todirections transverse to as well as transverse to and parallel to thedirection of propagation of the electromagnetic radiation beam (e.g.,x-direction variation, y-direction variation, and/or z-directionvariation). An initial scan pattern 510 can be configured so as toextend between two locations 512, 514 that are selected so that theinitial scan pattern 510 crosses a boundary 516 for an intraoculartarget for all expected variations in the location of the boundary 516.By processing the signal generated by the detection sensor 54 during theinitial scan pattern 510 along with focal point location data for theinitial scan pattern 510, a location 518 where the initial scan pattern510 crossed the boundary 516 can be identified.

A second scan pattern 520 can then be configured at least in part basedon the location 518. For example, end locations 522, 524 for the secondscan pattern 520 can be selected based on the location 518 so as to, forexample, substantially minimize the length of the second scan pattern soas to minimize the amount of tissue and/or material treated. Byprocessing the signal generated by the detection sensor 54 during thesecond scan pattern 520 along with focal point location data for thesecond scan pattern 520, a location 526 where the second scan pattern520 crossed the boundary 516 can be identified.

Any suitable subsequent scan pattern can be configured in a similarfashion. For example, by processing the signal generated by thedetection sensor during a scan pattern 530 along with focal pointlocation data for the scan pattern 530, a location 532 where the scanpattern 530 crossed the boundary 516 can be identified. End points 542,544 for a subsequent scan pattern 540 can be selected based on thelocation 532 so as to, for example, substantially minimize the length ofthe scan pattern 540 so as to minimize the amount of tissue and/ormaterial treated. Accordingly, a series of scan patterns can beadaptively configured and applied using boundary location data for theintraocular target generated from one or more previous scan patterns.

FIG. 20 illustrates a series of scan patterns 550 that can be used toincise a surface that transects a boundary 552 of an intraocular target.In the illustrated embodiment, the scan patterns 550 are adaptivelyconfigured using boundary location data generated from one or moreprevious scan patterns of the series of scan patterns 550, such asdescribed above with respect to FIG. 19 and method 500. Accordingly, theseries of scan patterns 550 can be configured to generally extend beyondboth sides of the boundary 552 by substantially uniform distances andthereby follow the general shape of the boundary 552.

FIGS. 21 and 22 illustrate scanning directions 554, 556 that can be usedto incise the series of scan patterns 550. While any suitable scanningdirections can be used, the illustrated directions 554, 556 can be usedto avoid having the electromagnetic radiation beam propagate throughpreviously treated tissue/material prior to reaching the focal point.

Corneal Incisions

The laser surgery system 10 can be configured to create different typesof corneal incisions including, for example, one or more arcuate (e.g.,relaxation) incisions, one or more cataract surgery primary accessincisions, and/or one or more cataract surgery secondary (sideport)incisions. Each of these types of corneal incisions can be made in oneor more different configurations.

FIGS. 23 through 25 illustrate aspects of arcuate incisions of a corneathat can be formed by the laser surgery system 10, in accordance withmany embodiments. FIG. 23 shows an en face view of arcuate incisionswithin the optical zone of the cornea that can be formed using the lasersurgery system 10. The optical zone can user-adjustable within, forexample, the range of 2 mm-11 mm. For asymmetric arcuate incisions, theoptical zone can be independently adjustable for each incision. Arclength can be user-adjustable within, for example, the range of10°-120°.

FIG. 24 shows a cross-sectional view of an arcuate incision in thecornea that can be formed using the laser surgery system 10 and thatpenetrates the cornea anterior surface and has an uncut posteriorportion. FIG. 25 shows a cross-sectional view of an arcuate intrastromalincision in the cornea that can be formed using the laser surgery system10. The arcuate intrastromal incision has an uncut anterior portion andan uncut posterior portion. Side cut angle can user-adjustable within,for example, the range of 30°-150°. Uncut posterior and anteriorportions can be user-adjustable within, for example, the range of 100μm-250 μm or 20%-50% of the cornea thickness. Cornea thickness can bemeasured at the projected intersection of the incision with the corneaanterior/posterior measured at 90° to anterior/posterior cornea surfaceregardless of what side cut angle is chosen.

FIG. 26 shows an en face view of a primary cataract incision in thecornea that can be formed using the laser surgery system 10. The primarycataract incision provides access to surgical tools used to, forexample, remove a fragmented crystalline lens nucleus and insert an IOL.FIG. 27 shows a cross-sectional view of a primary cataract incision ofthe cornea that can be formed using the laser surgery system 10. Limbusoffset can be user-adjustable within, for example, the range of 0.0mm-5.0 mm. Width can be user-adjustable within, for example, the range0.2 mm-6.5 mm. Length can be user-adjustable within, for example, therange of 0.5 mm-3.0 mm. Side Cut Angle can be user-adjustable within,for example, the range of 30°-150°. Plane depth can be user-adjustablewithin, for example, the range of 125 μm-375 μm or 25%-75% of the corneathickness. Length can be defined as the en face view distance betweenthe projected incision intersection with the cornea anterior and thecornea posterior. FIG. 28 shows a cross-sectional view of a primarycataract incision that includes an uncut anterior portion. FIG. 29 showsa cross-sectional view of a primary cataract incision that includes anuncut posterior portion. FIG. 30 shows a cross-sectional view of aprimary cataract incision that includes an uncut central length. AndFIG. 31 shows a cross-sectional view of a primary cataract incision thatincludes no uncut portion. Side Cut Angle can be user-adjustable within,for example, the range of 30°-150°. Uncut central length can beuser-adjustable within, for example, the range of 25 μm-1000 μm.

FIG. 32 shows an en face view of a sideport cataract incision in thecornea that can be formed using the laser surgery system 10. Thesideport cataract incision provides access for surgical tools used, forexample, to assist in the removal of a fragmented crystalline lens. FIG.33 shows a cross-sectional view of a sideport cataract incision of thecornea that has an uncut posterior portion and can be formed using thelaser surgery system 10. Limbus offset can be user-adjustable within,for example, the range of 0.0 mm-5.0 mm. Width can be user-adjustablewithin, for example, the range 0.2 mm-6.5 mm. Length can beuser-adjustable within, for example, the range of 0.5 mm-3.0 mm. FIG. 34shows a cross-sectional view of a sideport cataract incision thatincludes an uncut anterior portion. FIG. 35 shows a cross-sectional viewof a sideport cataract incision that includes an uncut central length.And FIG. 36 shows a cross-sectional view of a sideport cataract incisionthat includes no uncut portion. Side Cut Angle can be user-adjustablewithin, for example, the range of 30°-150°. Uncut central length can beuser-adjustable within, for example, the range of 100 μm-250 μm or20%-50% of the cornea thickness. Cornea thickness can be measured at theprojected intersection location of the incision with the corneaanterior/posterior measured at 90° to the anterior/posterior corneasurface regardless of what side cut angle is chosen.

Real-Time Monitoring Based Intensity Control

The laser surgery system 10 can be configured to use real-timemonitoring to control the intensity of the electromagnetic radiationbeam. The real-time monitoring can include, for example, monitoring ofthe signal generated by the detection sensor 54 of the confocal imagingassembly 14 and/or monitoring a sensor (e.g., a microphone) configuredto detect specific target structures or the occurrence of a cavitationevent.

FIG. 37 is a simplified block diagram of acts of a method 600 forcontrolling the intensity of an electromagnetic radiation beam used tomodify an intraocular target (e.g., tissue, IOL). The method 600 can beaccomplished, for example, using any suitable system including anysuitable laser surgery system described herein such as the laser surgerysystem 10.

The method 600 includes comparing a signal indicative of the intensityof a portion of an electromagnetic radiation beam reflected from a focalpoint to an operative range for modifying an intraocular tissue withoutgeneration of plasma and associated cavitation event (act 602). Thesignal can be generated, for example, by the detection sensor 54 of thelaser surgery system 10. If the comparison indicates that the intensityof the electromagnetic beam is outside of the operative range (10 microjoules for example), the intensity of the electromagnetic radiation beamis adjusted to be within the operative range (act 604).

FIG. 38 is a simplified block diagram of acts of a method 610 forcontrolling the intensity of an electromagnetic radiation beam used tomodify an intraocular target (e.g., tissue, IOL). The method 610 can beaccomplished, for example, using any suitable system including anysuitable laser surgery system described herein such as the laser surgerysystem 10.

The method 610 includes monitoring an intraocular target for anoccurrence of a cavitation event generated by the electromagneticradiation beam used to modify the intraocular target (act 612). Forexample, the signal generated by the detection sensor 54 of the lasersurgery system 10 can be monitored for the occurrence of a cavitationevent in the intraocular target. This would lead to an increasedconfocal signal reflection from the eye that may indicate an overtreatment. In such a case, the laser pulse energy can be automaticallyreduced by the control electronics 304. The laser surgery system 10 canalso incorporate a sensor (e.g., a microphone) configured to detect theoccurrence of a cavitation event in the intraocular target. If anoccurrence of a cavitation event in the intraocular target is detected,the intensity of the electromagnetic radiation beam is reduced (act614).

Posterior Capsulotomy Through an IOL

In some instances, the posterior portion of a lens capsule of apatient's eye may become at least partially opaque subsequent to theinstallation of an intraocular lens (IOL). In such instances, it may bepreferable to perform a posterior capsulotomy through the IOL to avoidremoval of the IOL. In many embodiments, the laser surgery system 10 canbe configured to perform a posterior capsulotomy through an IOL. Forexample, the laser surgery system 10 using an electromagnetic radiationbeam having a wavelength between 320 nm to 430 nm can be used to performa posterior capsulotomy through an IOL made from a material sufficientlytransmissive of the wavelength used. While any suitable electromagneticradiation beam of any suitable wavelength can be used, a wavelengthbetween 320 nm to 430 nm can be used to maximize scattering of theelectromagnetic radiation beam by the vitreous so as to minimizepossible damage to the retina.

FIG. 39 illustrates an IOL 620 positioned in a lens capsule 622 and anadjacent portion of the anterior hyaloid surface 624 of the vitreous626. To avoid damage to the anterior hyaloids surface 624 so as to avoidcompromising containment of the vitreous 626, the anterior hyaloidsurface 624 can be separated and displaced relative to the posteriorportion of the lens capsule 622 using any suitable approach. Forexample, a suitable fluid can be injected into the eye forward of theanterior hyaloid surface so as to separate the anterior hyaloid surfacefrom the posterior portion of the lens capsule 622. FIG. 40 illustratesthe adjacent portion of the anterior hyaloid surface 624 displacedrelative to the IOL 624 and a closed boundary incision surface 628transecting the posterior portion of the lens capsule 622. The closedboundary incision surface 628 can be formed using any suitable system ormethod, including those described herein such as the laser surgerysystem 10. For example, the closed boundary incision surface 628 can beformed using concurrent imaging and adaptive tissue treatment asdescribed herein so as to reduce the extent by which the closed boundaryincision surface extends on one or both sides of the posterior portionof the lens capsule 622 so as to reduce the probability of damaging theanterior hyaloid surface 624 and/or the IOL 620.

Refractive Correction Via Laser-Induced Modification of Refractive Indexof an IOL

As described herein, the laser surgery system 10 can be used to modifyeye tissue (e.g., corneal tissue) without generating plasma andassociated cavitation event. The laser eye surgery system 10 can also beused to modify an IOL in situ without generating plasma and associatedcavitation event. FIG. 41 illustrates an IOL 630 that has been modifiedby using the laser eye surgery system 10 to induce a plurality of smalllocalized modification 632. In many embodiments, the small localizedmodifications 632 are accomplished so as to change the refractive indexof the IOL material within the small localized modifications 632. Suchlocalized modification of refractive index can be used to controllablyconfigure the refractive index profile of the IOL 630 so as to impose adesired refractive correction without removal of the IOL 630 from thepatient's eye. Suitable IOL targets include acrylic IOLs or in generalall materials that have at least some transmission of the laserwavelength to enable the modification. Other IOL materials are feasibleas long as suitable transmission is provided. Modification of therefractive index may be in the order of about 10%, so in the case ofacrylic with an index of refraction of 1.4914 it may be modified to havean index of refraction of about 1.6405 or to about 1.3423.

Lens Fragmentation

The laser surgery system 10 can be configured incise a crystalline lens.For example, the electromagnetic radiation beam 28 generated by thelaser assembly 12 can have a wavelength that is suitably transmissibleby the crystalline lens, such as, for example, a wavelength between 800nanometers and 1100 nanometers.

FIG. 42 shows a capsulotomy incision designator 422 and a fragmentationboundary designator 640, in accordance with many embodiments, overlaidon a plan view of an eye that shows the location of the limbus 642 andthe pupil 644. In many embodiments, each of the capsulotomy incisiondesignator 422 and the fragmentation boundary designator 640 ispositioned and sized to maintain at least a minimum suitable safeworking distance from the pupil 644 to avoid having the electromagneticradiation beam 28 be incident on the pupil 644 to avoid associateddamage of the pupil 644. Accordingly, the fragmentation boundarydesignator 640 can be used in conjunction with the pupil 644 todetermine a corresponding iris safety margin distance.

FIG. 43 shows a cross-sectional diagram of an eye that illustrates alens fragmentation volume 646 defined to maintain an anterior safetymargin distance 648 from the anterior portion of the lens capsule 418,an iris safety margin distance 650 from the pupil 644, and a posteriorsafety margin distance 652 from the posterior portion of the lenscapsule 418. As described herein, the laser surgery system 10 can beused to identify the location of a boundary of an intraocular target,and can be configured to identify a suitable set of locations on theanterior and posterior lens capsule. For example, the focal point can bescanned using a low imaging-only power level (e.g., a power levelsufficient to locate a suitable set of locations on the anterior andposterior portions of the lens capsule 418 via processing of the signalgenerated by the detection sensor 54 of the confocal detection assembly14 without modifying eye tissue) along a suitable path selected to crossthe anterior and/or posterior portion of the lens capsule 418 to locatepositions on the lens capsule 418 at a sufficient number of locations tosupport definition of the lens fragmentation volume 646.

Referring now to FIG. 44, in many embodiments, the laser surgery system10 is configured to create a pattern of intersecting incisions 654within the lens fragmentation volume 646 so as to fragment the lenswithin the lens fragmentation volume 646 into discrete fragmentsconfigured (e.g., sized, shaped) for subsequent removal from the lenscapsule 418. While any suitable lens fragmentation parameters can beemployed, example lens fragmentation parameters, including fragmentationpatterns, cut dimensions for lens segmentation and softening, lasersettings, and applicable safety margins, are illustrated in FIG. 45 andprovided in Tables 1 and 2.

TABLE 1 User-adjustable Lens Fragmentation Parameters Feature DefaultRange Step Size Units Diameter * 3.0-10.0 0.5 mm Horizontal Spot Spacing10 5-25 2.5 μm Vertical Spot Spacing 40 10-100 10 μm Pulse Energy,Anterior** 8 1-10 0.5 μJ Pulse Energy, Posterior** 10 1-10 0.5 μJSeg-Soft Spacing 500 100-1500 100 μm Grid Spacing 500 100-2000 100 μm *Default diameter is defined by available pupil diameter - 2 * safetymargin. **Pulse energy to vary stepwise (linear) from posterior toanterior, if different

TABLE 2 Lens Fragmentation Safety Margins Feature Default Range StepSize Units Iris 500 N/A N/A μm Anterior*** 500 200-1000 100 μmPosterior*** 500 500-1000 100 μm ***Safety margins follow lens surfacecontours.

Corneal Flaps

In many embodiments, the laser surgery system 10 is configured to incisecorneal flaps. Referring now to FIG. 46 through FIG. 49, a corneal flap660 prepared in accordance with many embodiments is shown. The flap 660can be prepared in any suitable sequence. For example, the flap 600 canbe prepared by first using the laser surgery system 10 to laser incise aposterior surface 662 for the flap 660. The posterior surface 662 canhave any suitable configuration. For example, the posterior surface 662can have a perimeter that is a curved line centered approximately on theoptical axis 663 of the eye 24 and extending through an arc of about twohundred and seventy degrees. With the posterior surface 662 established,the laser surgery system 10 can be used to form an incision extendingfrom the anterior surface 664 of the cornea 24 to the perimeter of theposterior surface 662 to establish an edge 666 for the flap 660. Oncethe edge 666 is incised, the flap 30 can be raised to expose a bed ofstromal tissue 668. After exposure, the bed of stromal tissue 668 canbe, for example, photoablated using an excimer laser (not shown). Afterphotoablation with the excimer laser, the flap 660 can be repositionedover the bed of stromal tissue 668 and allowed to heal. The result is areshaped cornea 24.

Intra-Stromal Corneal Incisions

In many embodiments, the laser surgery system 10 is configured to createintra-stromal corneal incisions that can, for example, be used tocorrect refractive errors. For example, FIG. 50 is a cross-sectionalview of a cornea illustrating an incised volume 670 that is separatedfrom surrounding intra-stromal tissue of the cornea by enclosingincision surfaces created by the laser surgery system 10. Theillustrated incised volume 670 is axially-symmetric about the opticalaxis of the eye. The laser surgery system 10 can be used to form anaccess incision 672 of suitable configuration to allow removal of theincised volume 670. Removal of the incised volume 670 results inreshaping of the cornea so as to modify the refractive properties of thecornea. One or more incised volumes of any suitable configuration can beincised and removed to reshape the cornea so as to modify the refractiveproperties of the cornea. For example, the incised volume 670illustrated in FIG. 50 is configured to modify the refractive propertiesof the cornea to correct myopia. As another example, FIG. 51 illustratesan annularly-shaped incised volume 674 that can be laser incised by thelaser surgery system 10 and then removed to reshape the cornea tocorrect hyperopia. The illustrated incised volume 674 isaxially-symmetric about the optical axis of the eye. One or moreadditional incisions can be laser formed by the laser surgery system 10to divide the incised volume 670, 674 into suitably sized portions tofacilitate their removal. While the illustrated incised volumes 670, 674are both axially-symmetric and configured to correct myopia andhyperopia, respectively, any other suitably configured incised volume(s)can be incised so as to effect a desired reshaping of the corneacorresponding to a desired refractive modification of the cornea.

Corneal Inlay Pockets

Referring now to FIG. 52 and FIG. 53, which show a cross-sectional viewand a plan view of a cornea, respectively, the laser surgery system 10can be configured to create an intra-stromal pocket 680 in a cornea. Theintra-stromal pocket 680 is configured to accommodate an insertedintra-stromal inlay. The intra-stromal pocket 680 is defined by one ormore intra-stromal incision surfaces 682, 684 that are laser incised bythe laser surgery system 10. For example, the intra-stromal pocket 680can be defined by a single incision surface 682 (e.g., a circular planarintra-stromal incision) configured to accommodate and position aninserted intra-stromal inlay. The intra-stromal pocket 680 can also bedefined by incising a volume and removing the incised volume to leave athree-dimensional intra-stromal pocket configured to accommodate andposition an inserted intra-stromal inlay. For example, the intra-stromalpocket 680 can be defined by incising a volume bounded by theillustrated incision surfaces 682, 684, both of which areaxially-symmetrically shaped relative to the visual axis of the eye. Thelaser surgery system 10 can be used to create an access incision 686that extends from the intra-stromal pocket 680 insertion to the anteriorsurface of the cornea. The combination of the intra-stromal pocket 680and the access incision 686 has an intra-stromal perimeter 688 and anexposed perimeter 690 disposed on the anterior surface of the cornea. Anintra-stromal inlay can then be inserted into the intra-stromal pocket680 through the access incision 686 without the creation of a fullcorneal flap.

The intra-stromal pocket 680 can be formed so as to accommodate andposition and/or orient any suitable intra-stromal inlay. For example,the intra-stromal pocket 680 can have a circular perimeter and beconfigured to accommodate and position a correspondingly sized circulardisk-shaped intra-stromal inlay. As another example, the intra-stromalpocket 680 can have a non-circular perimeter of any suitable shape(e.g., ellipse, rectangular, polygonal) and be configured toaccommodate, position, and orient a correspondingly sized and shapedintra-stromal inlay, thereby controlling the angular orientation of theinserted intra-stromal inlay relative to the optical axis of the eye.Such control of angular orientation of the inserted intra-stromal inlaycan be used to, for example, treat astigmatism. An example of anintra-stromal inlay for which the laser assembly 10 can create acorresponding intra-stromal pocket 680 includes an opaque circularmicro-disc with a small opening in the center, for example, the KAMRA™inlay.

DSEK/DMEK/DALK and PK Incisions

The laser surgery system 10 can be configured to create corneal surgicalincisions such as Descemet's Stripping Endothelial Keratoplasty (DSEK),Descemet's Membrane Endothelial Keratoplasty (DMEK), Deep AnteriorLamellar Keratoplasty (DALK), and/or Penetrating Keratoplastic (PK).DSEK, DMEK, DALK, and PK corneal incisions are used to treat cornealdiseases in which one or more portions of the cornea are dysfunctionaland are surgically removed and exchanged. Because the laser surgerysystem 10 is operable to form precise corneal incisions, better clinicalresults and better patient satisfaction may result with regard to DSEK,DMEK, DALK, and/or PK corneal incisions as compared to less preciseapproaches.

Enhanced Patient Clearance

Referring now to FIG. 54, in many embodiments of the laser surgerysystem 10, the scanning assembly 18 and the objective lens assembly 20are configured to provide a clearance 700 (e.g., between 100 and 250millimeters in many embodiments with the illustrated clearance beingapproximately 175 millimeters) between the scanning assembly 18 and thepatient 24 without using a lens relay. The clearance 700 is achieved byutilizing an optical design that is constrained by target physical sizeparameters while being configured to create precise incisions within adesired scan volume without using a lens relay. The clearance 700 isdesirable for both the physician and the patient. For the physician,adequate clearance enhances visibility of the patient during the patientdocking process, and provides room for the physician to grasp theobjective lens assembly 20 directly for easy manipulation of theposition of the objective lens assembly 20 relative to the patient. Forthe patient, the clearance 700 may help reduce the possibility ofexcessive patient movement that may arise due to patient anxietystemming from a claustrophobic reaction to the proximity of the scanningassembly 18.

Significant design parameters relative to the configuration of thescanning assembly 18 and the objective lens assembly 20 include thedesired scan volume (e.g., desired cut radius at each of various depthswithin the patient's eye), the strehl ratio (laser focused spotquality), telecentricity, desired patient clearance, number of opticalelements (lenses), and not utilizing a lens relay. By balancing theseparameters, a patient clearance of approximately 175 millimeters andobjective lens housing of approximately 60 millimeters in diameter wereachieved. An important aspect to achieving an efficient configurationfor objective lens assembly 20 without the use of a lens relay is theuse of a small number of high optical power negative and positivelenses. In the illustrated embodiment, the objective lens assembly 20does not utilize a lens relay, which would require a larger number oflenses and create a patient clearance far in excess of that required toprovide adequate access for the physician and of that required toadequately reduce patient discomfort due to a claustrophobic reaction tothe proximity of the instrument. In contrast, FIG. 55 illustrates anobjective lens assembly 704 that utilizes a lens relay (as evidenced bybeam cross-over locations 706, 708) and has a clearance 710 ofapproximately 340 mm, which exceeds the clearance 700 of between 100 and250 mm and is thus significantly beyond a presently preferred range ofclearances for this application.

In many embodiments, the scanning assembly 18 is also configured tominimize the diameter of the objective lens housing. For example, inmany embodiments, the scanning assembly 18 includes an xy-scan device60, which is operable to deflect the beam 28 in two dimensionstransverse to the direction of propagation of the beam 28. In manyembodiments, the xy-scan device 60 includes a single deflectable mirrorthat is controllably deflectable to scan the beam 28 in two dimensionstransverse to the direction of propagation of the beam 28. By using asingle mirror as opposed to two or more mirrors, the diameter of theobjective lens housing can be reduced due to the ability to avoidadditional transverse displacement of the beam 28 associated with theuse of two or more scanning mirrors.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A laser eye surgery system comprising: an eyeinterface device configured to interface with an eye of a patient; anobjective lens; a scanning assembly configured to support the objectivelens and the eye interface device and to scan a focal point of a firstand a second laser beam to different target locations within the eye inx, y and z orthogonal directions; a laser beam source configured togenerate the first and second laser beams for imaging the eye andperforming the laser eye surgery; wherein the scanning assembly, theobjective lens and the eye interface device are configured to resttogether on the eye, to freely move together relative to the laser beamsource in the x, y and z directions and to follow together acorresponding free movement of the patient in the x, y and z directions;a free-floating mechanism that supports the scanning assembly and isconfigured to accommodate the free movement of the scanning assemblyrelative to the laser beam source in a manner that maintains alignmentin the x, y and z directions between the first and second laser beamsand the target locations during the free movement, the free-floatingmechanism including first and second beam deflection devices configuredto slide relative to one another in at least the z direction to vary adistance in the z direction between the first and second beam deflectiondevices, the first and second beam deflection devices being external tothe scanning assembly and located on an optical path between the laserbeam source and the scanning assembly, the first beam deflection devicearranged to receive the first and second laser beams in a firstdirection and deflect it to a second direction, and the second beamdeflection device arranged to receive the laser beam in the seconddirection and deflect it to a third direction, wherein the seconddirection is the z direction, and the first and third directions are thex or y direction, the second beam deflection device arranged to receivea reflection of a portion of the first laser beam from the focal pointlocation propagating in a direction opposite to the third direction anddeflect it to a direction opposite to the second direction, the firstbeam deflection device being disposed to receive the portion of theelectromagnetic radiation beam propagating in the direction opposite tothe second direction and deflect it to a direction opposite to the firstdirection; and a detection assembly configured to generate an intensitysignal indicative of intensity of the reflection of the portion of thefirst laser beam; a controller configured to scan the focal point of thesecond laser beam within the eye to create a corneal or capsularincision in the eye.
 2. The system of claim 1, wherein the first andsecond beam deflection devices are configured to have a variablerotational orientation.
 3. The system of claim 2, wherein thefree-floating mechanism further comprises a third beam deflection deviceconfigured to deflect the first and second laser beams propagating inthe third direction to propagate in a fourth direction different fromthe third direction, the third beam deflection device also beingconfigured to deflect the portion of the first laser reflected from thefocal point location and propagating opposite to the fourth direction topropagate opposite to the third direction, wherein the second and thirdbeam deflection devices are configured to have a variable distance orrotational orientation relative to one another.
 4. The system of claim1, wherein the detection assembly comprises a sensor configured togenerate the intensity signal and an aperture configured to blockportions of the laser beam reflected from locations other than the focalpoint from reaching the sensor.
 5. The system of claim 1, furthercomprising a polarization-sensitive device and a polarizing device, thepolarization-sensitive device being disposed along an optical path ofthe laser beam between the beam source and the free-floating mechanism,the laser beam passing through the polarization-sensitive device duringpropagation of the laser beam from the beam source to the free-floatingdevice, the polarizing device modifying polarization of at least one ofthe laser beam and a portion of the laser beam reflected from the focalpoint location, the polarization-sensitive device reflecting a portionof the laser beam reflected from the focal point to incident upon asensor configured to generate the intensity signal.
 6. The system ofclaim 5, wherein the polarizing device comprises a one-quarter waveplate.
 7. The system of claim 1, wherein the first laser beam has apower level lower than the second laser beam.
 8. The system of claim 1,wherein the second laser beam comprises a plurality of laser pulseshaving a wavelength between 320 nanometers and 430 nanometers.
 9. Thesystem of claim 1, wherein the second laser beam comprises a pluralityof laser pulses having a wavelength between 800 nanometers and 1100nanometers.
 10. The system of claim 1, wherein the second laser beamcomprises a plurality of laser pulses having a pulse duration of between100 femtoseconds and 15 nanoseconds.